Sheet metal forming processes are used to form a sheet metal stock into a desired shape and size. Sheet metal forming processes include but are not limited to stamping, pressing, and roll forming. Roll forming processes are typically used to form parts having a desired cross-section from a generally flat roll stock. In contrast to stamping processes, roll forming is well suited for use with high strength materials. Typical roll forming processes use a number of pairs of rotatable rolls. Each pair of rolls defines a particular cross-sectional shape that is imparted to the roll-stock as it passes through and is compressed between the rolls as they rotate. As the roll stock moves from one roll pair to the next, it is progressively formed into the desired cross-sectional shape. Because the roll stock is fed as a continuous length of steel, a cut-off press or similar device is used to separate each formed section into discrete parts. The process can be used to form a wide variety of parts, including automotive parts such as bumpers, door beams, and rocker panels.
Buyers of roll-formed parts, such as automotive OEMs, typically impose specifications on the cross-sectional profile of the parts. Such specifications are particularly important if the parts are intended to mate with other complementary parts because profile variations can prevent satisfactory alignment and mating. However, certain desirable roll forming stocks, such as high strength Martensite steels, have significant variations in their profiles, such as areas of concavity, convexity, bumps, or other profile distortions. Such profile variations in the roll-stock can make it difficult or impossible to meet the buyer's specifications for the finished part. Similar problems can arise in sheet metal stocks used for stamping and pressing operations. Accordingly, a need has arisen for a means of reducing profile variations in sheet metal stocks.